A large, randomized study led by a researcher in the UNC Gillings School of Global Public Health found that vitamin D and calcium supplements do not reduce the risk of colorectal adenomas, which are benign tumors that can evolve into colorectal cancer.
The results, published October 14 in the New England Journal of Medicine, came as a disappointment to the researchers. Previous observational studies had pointed to an association between lower colorectal cancer risk and higher vitamin D blood levels, and to lower colorectal cancer risk alongside increased calcium intake.
“There’s a lot of interest in vitamin D these days because of many positive findings in non-randomized studies,” explained the study’s lead author Dr. John Baron, research professor in the Gillings School and the UNC School of Medicine, and a member of the UNC Lineberger Comprehensive Cancer Center. “In particular, vitamin D has been investigated for its protective benefits against a range of diseases, including colorectal cancer.”
“We found that vitamin D and calcium supplements did not affect the occurrence of colon polyps, which are benign precursors to colorectal cancer. So our results came as a disappointment.”
Colorectal cancer is the fourth most common cancer in the United States, with an estimated 132,700 new cases and 49,700 deaths from the disease this year, according to NCI Surveillance, Epidemiology and End Results Program data. Colorectal cancers can develop from precancerous growths called adenomas.
The study included 2,259 people at 11 academic medical centers or affiliated medical practices. Patients recently diagnosed with precancerous adenomas, but who had no colorectal polyps remaining after a colonoscopy, were included.